12V to 120V Inverter

Have you ever wanted to run a TV, stereo or other appliance while on the road or camping? Well, this inverter should solve that problem. It takes 12 VDC and steps it up to 120 VAC. The wattage depends on which tansistors you use for Q1 and Q2, as well as how "big" a transformer you use for T1. The inverter can be constructed to supply anywhere from 1 to 1000 (1 KW) watts.

Important: If you have any questions or problems with the circuit, see the forum topic linked to in the Notes section. It will answer all your questions and provide links to many other (and better) inverter circuits.

Schematic

Parts

Part

Total Qty.

Description

Substitutions

C1, C2

2

68 uf, 25 V Tantalum Capacitor

R1, R2

2

10 Ohm, 5 Watt Resistor

R3, R4

2

180 Ohm, 1 Watt Resistor

D1, D2

2

HEP 154 Silicon Diode

Q1, Q2

2

2N3055 NPN Transistor (see "Notes")

T1

1

24V, Center Tapped Transformer (see "Notes")

MISC

1

Wire, Case, Receptical (For Output)

Notes

Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1,Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power.

The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger the microwave the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The guage of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. Thats all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055's in the parts list can only handle 15 amps each.

Since this project produces 120 VAC, you must include a fuse and build the project in a case.

You must use tantalum capacitors for C1 and C2. Regular electrolytics will overheat and explode. And yes, 68uF is the correct value. There are no substitutions.

This circuit can be tricky to get going. Differences in transformers, transistors, parts substitutions or anything else not on this page may cause it to not function.

If you want to make 220/240 VAC instead of 120 VAC, you need a transformer with a 220/240 primary (used as the secondary in this circuit as the transformer is backwards) instead of the 120V unit specified here. The rest of the circuit stays the same. But it takes twice the current at 12V to produce 240V as it does 120V.

Check out this forum topic to answer many of the most commonly asked questions about this circuit: 12 - 120V Inverter Again. It covers the most common problems encountered and has some helpful suggestions.

Comments

Hi,
what is the transformer part if I wan to buy a brand new part. I check in may website but cannot find any part similar to this that will be helpful?
what should I change if I need increase current flow in the power inverter?
thanks
hari

Not bad for a simple inverter--a least not if you don't mind a square-wave output, which is what you'll get out of this multivibrator-driven circuit. Not sure if I'd trust this to run any expensive electronics, though ...

hi,what if i wanted to modify a transformer with 230v input,how many turns in secondary & primary windings also does this circuit produce pure sine wave & if not how to make it produce it,lastly the capacitor issue are tgey correct or something cause i've read tgat otgers have their"s exploding & i dont like such situations.

i have made this circuit and its good. i have been updating some component to make it more good..
this is what i have to share..
If your making your own transformer for this project with the output of 230v or 240v... first you have to wind the secondary windings which is the 230v or 240v output. after you finish the first windings. take a secondary windings which is the output transistor is connected...
okay this is the explaination why the 220v first.
lets take first the input side of the transformer... to make the transistor will take not overload due to resistance. the transprmer will have to wind more to build additional resistance from the copper wire. due to this effeciency will take 80%-89% for the whole power has been transmitted to the other side of the transforme.

I found a good transformer at Radioshack for those who were looking for one. It's the 25.2V CT 2.0A Heavy-Duty Chassis-Mount Transformer with Lead item number 273-1512.
http://www.radioshack.com/product/index.jsp?productId=2102703
If the link doesn't work just search the item number.

If you would like to leave a comment, you can do so using the form below. Comments can be things like suggestions, successes or failures, improvements, similar circuits, error reports, an answer to a previous commenter's question, or anything in between. However if you would like to ask a question it is suggested that you use the forum instead. The forum provides a more robust environment for discussion.

Important: If you post a technical question here, there is no guarantee it will be answered. All technical questions should be posted to the forum. The owner of this site generally does not answer questions in comments.

All comments are subject to approval before they are displayed here, so your comment will not appear immediately. This is done mainly to prevent spam and other abuse. If you wish to remain anonymous, simply enter "anonymous" for your name and/or email.

Name:

Email:

Subject:

Comments:

Anti Spam Code:

Please enter the exact text shown in the image above into the box below.
Browser cookies must be enabled to comment on circuits.